Catalyst composition

Abstract

A method for producing an exhaust gas purifying catalyst including a composite oxide represented by the following general formula (3), the method including a primary baking step of baking a coprecipitate obtained from an aqueous mixed salt solution of respective elements, a citrate complex obtained from an aqueous citric acid mixed salt solution of salts of the respective elements and citric acid, or a precipitate obtained from an alkoxide mixed solution of the respective elements at 500 to 1200° C., the respective elements constituting the exhaust gas purifying catalyst represented by the following general formula (3), including A, B and Fe but excluding Pd; a step of adding an aqueous solution of Pd salt to a primary composite oxide obtained through the primary baking step to give a precursor composition; and a secondary baking step of baking the precursor composition at 800 to 1400° C., AO.x(B 2-y-Z Fe y Pd Z O 3-α ) (3).

1 .- 11 . (canceled) 
     
     
         12 . A method for producing an exhaust gas purifying catalyst comprising a composite oxide represented by the following general formula (3), the method comprising:
 a primary baking step of baking a coprecipitate obtained from an aqueous mixed salt solution of respective elements, a citrate complex obtained from an aqueous citric acid mixed salt solution of salts of the respective elements and citric acid, or a precipitate obtained from an alkoxide mixed solution of the respective elements at 500 to 1200° C., the respective elements constituting the exhaust gas purifying catalyst represented by the following general formula (3), including A, B and Fe but excluding Pd;   a step of adding an aqueous solution of Pd salt to a primary composite oxide obtained through the primary baking step to give a precursor composition; and   a secondary baking step of baking the precursor composition at 800 to 1400° C.,
   AO.x(B 2-y-z Fe y Pd Z O 3-α )  (3)
 
   wherein A represents an element selected from monovalent elements, divalent elements, and rare earth elements, B represents Al, or Al and a transition element T; x represents 1 to 9; y represents an atomic ratio satisfying the following relation: 0<y≦1.2; z represents an atomic ratio satisfying the following relation: 0<z≦0.5; and α represents a deficient atomic ratio of oxygen atoms,   wherein T is selected from a group consisting of elements having atomic numbers of 21 (Sc) through 25 (Mn), atomic numbers of 27 (Co) to 30 (Zn), atomic numbers of 39 (Y) through 43 (Tc), atomic numbers of 47 (Ag) and 48 (Cd), atomic numbers of 57 (La) through 75 (Re), atomic numbers of 79 (Au) and 80 (Hg), and atomic numbers 89 (Ac) or higher.   
     
     
         13 . The method for producing an exhaust gas purifying catalyst according to  claim 12 , wherein the A is at least one element selected from the group consisting of alkali metals, alkaline earth metals, and rare earth elements. 
     
     
         14 . The method for producing an exhaust gas purifying catalyst according to  claim 13 , wherein the A is Mg. 
     
     
         15 . The method for producing an exhaust gas purifying catalyst according to  claim 12 , wherein the B is Al. 
     
     
         16 . The method for producing an exhaust gas purifying catalyst according to  claim 12 , wherein the x is 1 to 5. 
     
     
         17 . The method for producing an exhaust gas purifying catalyst according to  claim 16 , wherein the x is 1. 
     
     
         18 . The method for producing an exhaust gas purifying catalyst according to  claim 12 , wherein the z satisfies 0<z≦0.015.